The answer is to use AWS Managed Microsoft AD in the shared services account and set up a trust relationship with each developer account. This is the most secure approach because it establishes a one-way or two-way forest trust between the shared directory and a separate AWS Managed AD directory in each developer account, allowing EC2 instances in the developer VPCs to perform a cross-account domain join without directly exposing the shared directory across account boundaries. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of maintaining strict security boundaries while enabling centralized authentication, and the common trap is choosing a solution that uses IAM roles or VPC peering to directly access the shared AD, which violates the principle of least privilege. Remember the key distinction: trusts keep directories isolated, while direct access breaks security boundaries. Memory tip: "Trust, don't touch" — use forest trusts to keep shared AD secure across accounts.
SAP-C02 Practice Question: Design Solutions for Organizational Complexity
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a multi-account AWS environment with a shared services account that hosts Active Directory for authentication. Developers need to launch EC2 instances in development accounts and join them to the domain. What is the most secure way to allow this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Managed Microsoft AD in the shared services account and set up a trust relationship with each developer account
Option D is correct because AWS Managed Microsoft AD in the shared services account can establish a one-way or two-way forest trust with a separate AWS Managed Microsoft AD directory in each developer account. This allows EC2 instances in the developer VPCs to authenticate against the shared Active Directory without exposing the directory directly across accounts, maintaining security boundaries while enabling seamless domain join.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Establish VPC peering between the shared services VPC and each developer VPC
Why it's wrong here
Network connectivity alone is insufficient.
✗
Create a shared secret for the domain and store it in AWS Secrets Manager in each developer account
Why it's wrong here
Sharing secrets is insecure and not scalable.
✗
Use AWS Systems Manager to automate domain join with a custom document
Why it's wrong here
Systems Manager does not handle cross-account authentication natively.
✓
Use AWS Managed Microsoft AD in the shared services account and set up a trust relationship with each developer account
Why this is correct
Trust relationships allow domain join across accounts securely.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume VPC peering (Option A) is sufficient for cross-account domain join, but they overlook the need for a trust relationship between Active Directory domains and the complexities of DNS resolution across accounts.
Detailed technical explanation
How to think about this question
AWS Managed Microsoft AD supports forest trusts using Kerberos authentication over TCP/UDP port 88 and LDAP over TCP port 389. When setting up a trust between two AWS Managed Microsoft AD directories, you must ensure that the VPCs are connected via VPC peering or AWS Transit Gateway, and that DNS resolution is configured to forward queries between the directories. The trust relationship allows users from the shared services domain to authenticate to resources in the developer accounts without replicating user objects, which is critical for maintaining a single source of identity.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use AWS Managed Microsoft AD in the shared services account and set up a trust relationship with each developer account — Option D is correct because AWS Managed Microsoft AD in the shared services account can establish a one-way or two-way forest trust with a separate AWS Managed Microsoft AD directory in each developer account. This allows EC2 instances in the developer VPCs to authenticate against the shared Active Directory without exposing the directory directly across accounts, maintaining security boundaries while enabling seamless domain join.
What should I do if I get this SAP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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